Agitator tool

ABSTRACT

A rotatable agitator tool is disclosed for use with a pump mechanism, for agitating production fluid comprising sand or other debris and for breaking out solution gas, comprising an elongate shaft connected to a rotating element such as a rotor, and a plurality of agitation members extending outwardly from the elongate shaft, the agitator tool extending in an upstream direction from the pump mechanism. The agitation members are preferably flexible to allow the agitator tool to be pushed and pulled through a stator (where employed with a progressive cavity pump) without damaging the elastomeric coating on the stator.

FIELD OF THE INVENTION

The present invention relates to tools for use with hydrocarbon or water production, and more particularly to tools that are employed with pumping mechanisms.

BACKGROUND OF THE INVENTION

In the context of hydrocarbon or water production, conventional pumping means are of great utility where the production fluid is relatively clean and free of debris or other particulate matter. However, where debris or other particulate matter are present in the production fluid, conventional pumping means can experience failure. For example, production fluids may contain “sand slugs” which can be sucked into a pump mechanism intake and either cause “sanding” of the pump, requiring costly servicing, or plugging of the intake which results in hysteresis in progressive cavity pumps or other failures in the ability to produce fluids.

Also, gas lock can occur with progressive cavity (PC) pumps where entrained gas passes into the pump mechanism, comes out of solution and accumulates in the cavities; such gas lock may block the ability of the pump to pass fluids through the pump. Unless something intervenes to break the gas out of solution, allowing it to pass up the annulus of the wellbore, the gas will be drawn into the pump.

As production fluid may comprise a combination of oil, water, gas, sand and other particulates, these problems are of significant concern to companies involved in hydrocarbon production, as the problems can result in costly servicing and pump damage, not to mention the loss of operation efficiency and actual production.

Prior attempts to address these problems include the commercially-available Gizmo™ downhole agitator of Innovative Production Technologies Ltd., which agitator attaches to the bottom of a PC pump; one portion of the Gizmo™ is rotatable and mates with the rotor, while a stationary portion mates with the stator. A steel spring rotates past production ports in the Gizmo™ to agitate adjacent production fluids. It has been found that only limited agitation is generated, and the entire pump must be pulled if the agitator experiences wear. Also, the drive spear fastened to the rotor has been found to break in some instances, possibly due to the rotor eccentricity and oscillation, and the Gizmo™ itself can break off of the pump, requiring “fishing” efforts to remove any broken parts.

Another attempt to address these problems is the combination of a “paddle rotor” with a slotted tag bar, as manufactured by numerous companies. The paddle rotor has a flat portion on the rotor surface, such that landing the rotor in a slotted tag bar is alleged to generate a mixing action at the pump intake. This, too, has been found to produce only limited agitation.

As can be seen, therefore, a simple cost-effective solution to these continuing problems is still needed. What is required is an agitator tool that is cost-effective to produce and purchase, provides for ease of servicing, and generates substantial turbulent flow to break up particulate matter in production fluids, keep the particulate matter in suspension, and help break entrained gas out of solution so that it can migrate up the well annulus rather than enter the PC pump.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a rotatable tool for use with a pump mechanism, for agitating production fluid and breaking out entrained gas, comprising an elongate shaft, connecting means on the elongate shaft for connecting a downstream end of the elongate shaft to a rotating element of the pump mechanism, and at least one agitation member on and extending outwardly from the elongate shaft.

In exemplary embodiments of the present invention, the rotatable tool and pump mechanism are housed within a surface flowline or downhole casing, and can be housed within a tag bar adjacent the pump mechanism. The pump mechanism is preferably a progressive cavity pump (although other rotary pumps could be employed), wherein the rotating element is a rotor housed within a stator. The elongate shaft may be either straight or of irregular orientation along its length. The connecting means preferably comprise a slim-hole coupling welded to the downstream end of the elongate shaft, with a female thread in the slim-hole coupling and a corresponding male thread on an upstream end of the rotating element, although they may also comprise a quick-connect coupling enabling disengagement of the elongate shaft from the rotating element.

The at least one agitation member is preferably a plurality of bristles (which may be composed of nylon, steel or rubber) extending substantially perpendicular to the long axis of the elongate shaft (although other orientations may be desirable in different contexts) and connected to the elongate shaft by means of a casing wrapped around the elongate shaft, the casing connected to the elongate shaft by spot welds, and the bristles held in the casing by crimping of the casing around an inner end of the bristles. The plurality of bristles are most preferably folded around a wire core, the wire core located in the casing and sized to be held in the casing by the crimping of the casing. The casing may be in the form of a helical track of even or uneven phasing, and in the latter case the phasing may be closer adjacent the downstream end of the elongate shaft than adjacent the upstream end of the elongate shaft. The at least one agitation member is preferably adjacent an intake of the pump mechanism, and may be sized to enable contact of the at least one agitation member with at least a portion of inner walls of the surface flowline or downhole casing. Where a casing is employed to house the at least one agitation member, the rotatable tool may further comprise a first bushing connected to an upstream end of the elongate shaft and a second bushing connected to a downstream end of the elongate shaft by bushing welds for retaining the casing on the elongate shaft, and the spot welds and bushing welds are then preferably breakable to allow removal of the casing from the elongate shaft (for example, where the at least one agitation member has become worn and replacement is desirable). The at least one agitation member is preferably flexible to enable it to deform to be pulled through the stator where the rotating element is a rotor that can be pulled downstream of the stator.

According to a second aspect of the present invention there is provided a rotatable tool for use with a pump mechanism having a rotating element, for agitating production fluid and breaking out entrained gas, comprising an elongate shaft of unitary construction with the rotating element and extending upstream of the rotating element, and at least one agitation member on and extending outwardly from the elongate shaft.

According to a third aspect of the present invention there is provided a rotatable tool for use with a pump mechanism having a rotating element, for agitating production fluid and breaking out entrained gas, comprising an elongate shaft fixedly attached to the rotating element and extending upstream of the rotating element, and at least one agitation member on and extending outwardly from the elongate shaft.

According to a fourth aspect of the present invention there is provided a tool for use with a pump mechanism, for agitating production fluid and breaking out entrained gas, comprising an elongate shaft, connecting means on the elongate shaft for connecting a downstream end of the elongate shaft to the pump mechanism, and at least one agitation member on and extending outwardly from the elongate shaft. The pump mechanism according to this aspect is preferably a reciprocating pump.

An agitator tool in accordance with the present invention, therefore, can create strong turbulent flow to effectively agitate production fluid, keeping debris suspended in the emulsion while breaking out entrained gas, preventing pump intake plugging, agitating the wellbore sump, and keeping the production fluid energized. The agitator tool is cost-effective to produce, adaptable to pumps of different sizes, is easily installed, can be removed with the rod string due to bristle flexibility, and can have substantial bristle outer diameter (OD) due again to flexibility of the bristles.

A detailed description of an exemplary embodiment of the present invention is given in the following. It is to be understood, however, that the invention is not to be construed as limited to this embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which illustrate an exemplary embodiment of the present invention:

FIG. 1 is a side elevation view of an agitator tool according to the present invention, in a vertical orientation such as would be used in a downhole context, partially cut away at the first and second bushings to show the casing; and

FIG. 2 is a detailed sectional view of a helical casing holding bristles by means of crimping around a wire core.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

Referring now in detail to the accompanying drawings, there is illustrated an exemplary embodiment of the agitator tool according to the present invention, generally referred to by the numeral 10. The agitator tool 10, for use in surface flowlines or downhole casings (not shown), comprises an elongate shaft 12 having a downstream end 14 and an upstream end 16. The elongate shaft 12 is a 16″ 4140 steel shaft having an outer diameter OD₁ of ½″. The length of the elongate shaft 12 depends on how much sump is required or desired in a given context, and the outer diameter OD₁ and shaft geometry (for example, having a bend in the elongate shaft 12, or some other irregular form) can also be adjusted to address specific needs (the outer diameter OD₁ will depend to a large degree on the stator/rotor dimensions). Other materials can also be used to manufacture the elongate shaft 12. The elongate shaft 12 is welded to a slim-hole coupling 18 at the downstream end 14, the slim-hole coupling 18 housing female threads 20 for receipt of corresponding male threads on the upstream end of a rotor (not shown); the means for connecting the elongate shaft 12 to the rotation means will vary depending on such factors as the pump type, tubing inner diameter (ID), and stator ID. A first bushing 28 is positioned at the upstream end 16 of the elongate shaft 12 and welded thereto by a bushing weld 38 (a tap weld), while a second bushing 34 is positioned at the downstream end 14 of the elongate shaft 12 and similarly welded thereto by bushing weld 36. The first and second bushings 28, 34 are provided to assist in retaining the casing 24 on the elongate shaft 12, as described below.

A casing 24 in the form of a helical track is wrapped around the elongate shaft 12, secured to the elongate shaft 12 by means of spot welds 26. The spot welds 26 can be broken to allow removal of the casing 24 and repair/replacement thereof where, for example, the agitation members become worn (and the bushing welds are then also breakable). If the spot welds 26 were to fail, the first and second bushings 28, 34 are intended to retain the casing 24 on the elongate shaft 12. The first and second bushings 28, 34 are provided with set screws 40 which further serve to secure the casing 24 against the elongate shaft 12; although shown in FIG. 1 as simply inserted, the set screws 40 are preferably also welded at the heads and ground off. The casing 24 is a track ⅜″ in width and composed of galvanized or stainless steel, and is generally channel-shaped.

Bristles 22 are retained in the casing 24 by means of crimping, as can best be seen in FIG. 2 where the bristles 22 are held by means of crimps 30 (the crimps 30 formed from the arms of the channel shape). In the preferred embodiment, the bristles 22 are folded over a wire core 32, which wire core 32 is of diameter sufficient to be retained within the casing 24 once crimped, and the bristles 22 are thereby more firmly secured within the casing 24. The bristles 22 are positioned along almost the entire length of the casing 24 (a few empty courses of the casing 24 are provided at either end allowing smaller diameter bushings 28, 34 in the preferred embodiment), then essentially forming a helical or spiral brush in this exemplary embodiment, although other configurations are possible within the scope of the invention (although it is generally desirable to have at least some of the bristles 22 adjacent the pump intake). The bristles 22 are composed of nylon in this embodiment due to the inherent flexibility of the material, which allows the agitator tool 10 to be pulled through a stator (not shown) even though the outer diameter OD₂ of the agitator tool 10 with bristles 22 may be greater than the OD of the stator (in the illustration, the outer diameter OD₂ is 2¾″). The optional use of a tag bar (not shown) can also affect the outer diameter OD₂. The number and density of bristles 22 may be increased to enhance durability, and the material used for the bristles 22 may need to be varied in different contexts (such as highly corrosive downhole environments). In the illustrated embodiment, the bristles 22 are positioned generally perpendicular to the long axis of the elongate shaft 12, but various bristle angles may be employed where desired (for example, where an auguring effect is required), and even different angles for different courses on the same agitator tool 10.

The distance (“phasing”) “d” between the courses of the casing 24 can be adjusted to create different effects. While agitation of production fluid (not shown) is enhanced by a narrower phasing, as is demonstrated in the appended drawings (where distance “d” is relatively small and constant for all courses of the casing 24), auguring effects are enhanced by broader phasing. In certain instances it would be advantageous, therefore, to have a larger distance “d” between courses of the casing 24, or even a combination of narrow and broad phasing (or a continuum of narrow to broad) on the same agitator tool 10. For example, having broader phasing distant from the pump intake and narrower phasing adjacent the pump intake could produce an increasing auguring/agitation velocity as the production fluid draws nearer.

Where the bristles 22 are composed of stronger material, such as steel, it may be difficult to withdraw the agitator tool 10 out of the stator without damaging the elastomeric coating of the stator inner walls. In this case, it would be advantageous to house the agitator tool 10 in a tag bar (not shown) upstream and adjacent the pump mechanism, and employ a quick-connect coupling (not shown) to connect the rotor and elongate shaft 12. In this case, the rotor could be withdrawn from the stator by disconnecting the agitator tool 10 from the rotor and leaving the former within the tag bar.

While the exemplary embodiment described above has a threaded mating of the elongate shaft 12 and rotor by means of a slim-hole coupling 18, it may be desirable to have a permanent mating of the elongate shaft 12 and rotor, or even manufacture the elongate shaft 12 as an upstream extension of the rotor itself (unitary construction).

An agitator tool 10 constructed in accordance with the present invention was tested with a PC pump and proved highly effective in agitating production fluid. Debris, including sand slugs, was placed upstream of the agitator tool 10 in a test facility, and the sand slugs were decreased in size by approximately 60% before they could enter the pump intake, due to the agitation generated by the agitator tool 10. The risk of sand plugging the pump was therefore greatly minimized. Various sand concentrations were tested, and while pumps without the agitator tool 10 experienced operation difficulty when sand concentrations approached 40-50%, the agitator tool 10 was found to effectively address much higher concentrations and prevent operation difficulty. At greater rotational speeds, the agitator tool 10 could address very high sand concentrations due to the more vigorous agitation. In addition, use of the agitator tool 10 was found to create a cellar and clean perforated intervals. After testing, the agitator tool 10 was examined and no significant wear had occurred.

The present invention has demonstrated a broad range of utility, especially in downhole settings. Where a wellbore is known or found to generate production fluid comprising sand and/or solution gas, the agitator tool 10 can be used to break up sand slugs and break out some of the gas. In similar fashion, the present invention can also be used to prevent sand blockages in surface flowlines. However, the agitator tool 10 can also be used to clean out a PC pump by running the agitator tool 10 in and out of the stator (by extracting and inserting the rotor), which can assist in removing sand and debris from the elastomeric pump cavities. The agitator tool 10 can also be run above the pump with appropriate connection modifications, to agitate the production fluid and prevent settling of sand and debris that might otherwise cause sand/solids tubing bridges (blockages that inhibit discharge and prevent fluid movement to the surface, they can also cause high-pressure loading on the pump resulting in pump damage and premature failure); the agitator tool 10 can be run in series with appropriate connection modifications, as well, with no limit on the number of agitator tools 10 that could be run in a string above the pump, even to the surface. If the outer diameter OD₂ is great enough to reach the inner walls of the surface flowline or downhole casing, it can be used to clean the inner walls; this is especially useful in the downhole context, where the perforated interval can be kept clean by the agitator tool 10. Sump cleaning is also possible with the present invention, keeping clean an area roughly equal to the length of the agitator tool 10 (with various lengths being possible). Finally, it is also possible to use the present invention with coiled tubing for wellbore clean-outs. The present invention can therefore be run below, within, or above a pump mechanism, alone or in series, with varying utility in varying contexts. Also, its utility is not dependent on rotation of the agitator tool 10 in all instances, as it could be run, for example, with a reciprocating pump without any rotation.

While a particular embodiment of the present invention has been described in the foregoing, it is to be understood that other embodiments are possible within the scope of the invention and are intended to be included herein. It will be clear to any person skilled in the art that modifications of and adjustments to this invention, not shown, are possible without departing from the spirit of the invention as demonstrated through the exemplary embodiment. For example, the agitation members may be rubber “fingers” instead of nylon bristles, which are also flexible and can effectively agitate production fluid. Also, the agitation members could be housed in a series of stacked circular casings rather than a single helical casing, or the agitation members could be directly connected to the elongate shaft. As stated above, many of the dimensions and configurations will be context-dependent, which would be clear to one skilled in the art. The invention is therefore to be considered limited solely by the scope of the appended claims. 

1. A rotatable tool for use with a pump mechanism,for agitating production fluid and breaking out entrained gas, comprising: an elongate shaft; connecting means on the elongate shaft for connecting a downstream end of the elongate shaft to a rotating element of the pump mechanism; and at least one agitation member on and extending outwardly from the elongate shaft.
 2. The rotatable tool of claim 1 wherein the rotatable tool and pump mechanism are housed within a surface flowline or downhole casing.
 3. The rotatable tool of claim 1 wherein the pump mechanism is a progressive cavity pump.
 4. The rotatable tool of claim 3 wherein the rotating element is a rotor housed within a stator.
 5. The rotatable tool of claim 1 wherein the connecting means comprise a slim-hole coupling welded to the downstream end of the elongate shaft.
 6. The rotatable tool of claim 1 wherein the at least one agitation member is a plurality of bristles.
 7. The rotatable tool of claim 6 wherein the plurality of bristles are connected to the elongate shaft by means of a casing wrapped around the elongate shaft, the casing connected to the elongate shaft by spot welds, and the bristles held in the casing by crimping of the casing.
 8. The rotatable tool of claim 7 wherein the casing is a helical track.
 9. The rotatable tool of claim 1 wherein the at least one agitation member extends substantially perpendicular to the long axis of the elongate shaft.
 10. The rotatable tool of claim 6 wherein the plurality of bristles are composed of nylon.
 11. The rotatable tool of claim 7 further comprising a first bushing connected to an upstream end of the elongate shaft and a second bushing connected to a downstream end of the elongate shaft by bushing welds for retaining the casing on the elongate shaft.
 12. The rotatable tool of claim 11 wherein the spot welds and bushing welds are breakable to allow removal of the casing from the elongate shaft.
 13. The rotatable tool of claim 8 wherein the helical track is of even phasing.
 14. The rotatable tool of claim 8 wherein the helical track is of uneven phasing.
 15. The rotatable tool of claim 14 wherein the phasing is closer adjacent the downstream end of the elongate shaft than adjacent the upstream end of the elongate shaft.
 16. The rotatable tool of claim 1 wherein the at least one agitation member is adjacent an intake of the pump mechanism.
 17. The rotatable tool of claim 2 wherein the at least one agitation member is sized to enable contact of the at least one agitation member with at least a portion of inner walls of the surface flowline or downhole casing.
 18. The rotatable tool of claim 1 wherein the at least one agitation member is flexible.
 19. The rotatable tool of claim 4 wherein the at least one agitation member is flexible and can deform to be pulled through the stator when the rotor is pulled downstream of the stator.
 20. The rotatable tool of claim 5 wherein the connecting means are a female thread in the slim-hole coupling and a corresponding male thread on an upstream end of the rotating element.
 21. The rotatable tool of claim 1 wherein the elongate shaft is substantially straight along its length.
 22. The rotatable tool of claim 1 wherein the elongate shaft is of irregular orientation along its length.
 23. The rotatable tool of claim 1 wherein the connecting means comprise a quick-connect coupling enabling disengagement of the elongate shaft from the rotating element.
 24. The rotatable tool of claim 7 wherein the plurality of bristles are folded around a wire core, the wire core located in the casing and sized to be held in the casing by the crimping of the casing.
 25. The rotatable tool of claim 1 wherein the rotatable tool is housed within a tag bar adjacent the pump mechanism.
 26. A rotatable tool for use with a pump mechanism having a rotating element, for agitating production fluid and breaking out entrained gas, comprising: an elongate shaft of unitary construction with the rotating element and extending upstream of the rotating element; and at least one agitation member on and extending outwardly from the elongate shaft.
 27. A rotatable tool for use with a pump mechanism having a rotating element, for agitating production fluid and breaking out entrained gas, comprising: an elongate shaft fixedly attached to the rotating element and extending upstream of the rotating element; and at least one agitation member on and extending outwardly from the elongate shaft.
 28. The rotatable tool of claim 6 wherein the plurality of bristles are composed of steel.
 29. The rotatable tool of claim 6 wherein the plurality of bristles are composed of rubber.
 30. A tool for use with a pump mechanism, for agitating production fluid and breaking out entrained gas, comprising: an elongate shaft; connecting means on the elongate shaft for connecting a downstream end of the elongate shaft to the pump mechanism; and at least one agitation member on and extending outwardly from the elongate shaft.
 31. The tool of claim 30 wherein the pump mechanism is a reciprocating pump. 